diff options
Diffstat (limited to 'llvm/lib/Transforms')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp | 20 |
1 files changed, 16 insertions, 4 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp index 936daa828a5..18a2b2fdbfe 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp @@ -314,11 +314,22 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, Known.One = std::move(IKnownOne); break; } - case Instruction::Select: - // If this is a select as part of a min/max pattern, don't simplify any - // further in case we break the structure. + case Instruction::Select: { Value *LHS, *RHS; - if (matchSelectPattern(I, LHS, RHS).Flavor != SPF_UNKNOWN) + SelectPatternFlavor SPF = matchSelectPattern(I, LHS, RHS).Flavor; + if (SPF == SPF_UMAX) { + // UMax(A, C) == A if ... + // The lowest non-zero bit of DemandMask is higher than the highest + // non-zero bit of C. + const APInt *C; + unsigned CTZ = DemandedMask.countTrailingZeros(); + if (match(RHS, m_APInt(C)) && CTZ >= C->getActiveBits()) + return LHS; + } + + // If this is a select as part of any other min/max pattern, don't simplify + // any further in case we break the structure. + if (SPF != SPF_UNKNOWN) return nullptr; if (SimplifyDemandedBits(I, 2, DemandedMask, RHSKnown, Depth + 1) || @@ -336,6 +347,7 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, Known.One = RHSKnown.One & LHSKnown.One; Known.Zero = RHSKnown.Zero & LHSKnown.Zero; break; + } case Instruction::ZExt: case Instruction::Trunc: { unsigned SrcBitWidth = I->getOperand(0)->getType()->getScalarSizeInBits(); |
